Enhancement of antioxidant properties of Eisenia bicyclis extracts through combination of green extractions: Parameter optimization and comparison

We compared and optimized combined green extraction (CGE) technologies to maximize the antioxidant activity of Eisenia bicyclis through response surface methodology (RSM). Firstly, conventional extraction (CE), microwave assisted extraction (MAE), and supercritical fluid extraction by carbon dioxide (SFE-CO₂) were applied to extract and compare antioxidant activities of E. bicyclis. The antioxidant activity results indicated that MAE and SFE-CO₂ were superior to CE alone. Based on the optimum conditions for MAE and SFE-CO₂, ultrasound-assisted extraction (UAE) and high-pressure processing (HPP) were combining to increase antioxidant activity. SFE-CO₂+UAE was selected as the optimum CGE technology. The DPPH-radical scavenging activity and the total phenolic content of E. bicyclis extracts using SFE-CO₂+UAE were approximately 2 and 5-fold higher than those of extracts using CE with almost 9-fold higher dieckol content. We demonstrated that E. bicyclis has substantial potential as a natural antioxidant and that CGE is more effective than CE and GE in enhancing antioxidant yields.